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2. Every so often, try to poll the service (check it using the appropriate protocol). 3. If something doesn’t respond correctly, sound the alarm (via pager, email, and so on). This is actually a pretty cool way of monitoring your services; after all, SNMP might be working, but in the final analysis, you want to know that your service is working. Who cares if SNMP thinks that your Web server is up? If it’s not actually responding to the service when a network station tries it, it might as well be a boat anchor! Many third-party packages are available; some monitor whether generic TCP sockets are “alive and listening,” whereas others are complex utilities that are designed to monitor specific applications such as email or network databases. Previous Table of Contents Next
Previous Table of Contents Next Here are some examples of service monitoring packages, listed from the primitive to the sublime: • Sitter (ftp://feldman.org/pub/sitter) A primitive Linux bash script that checks ports using the Telnet trick and complains to the console when problems are found. This definitely must be manually reconfigured for your site. • Netoscope (http://www.basta.com) A Windows utility for checking socket availability of certain servers. Issues audible alerts or runs a program (such as email) when problems occur. • IPSentry (http://www.ipsentry.com) A socket-monitoring package that runs under Windows. It tries whichever IP addresses and sockets you want, as often as you like. It can also page you when a problem occurs. • WhatsUp and WhatsUp Gold (http://www.ipswitch.com) This is a graphical network polling package with paging features. WhatsUp Gold has Web access, SNMP features, and IPX monitoring, as well. WhatsUp Gold also has the dubious distinction of being quite expensive for a polling package (close to $1,000 at this writing). So when do you use “pollsters” rather than SNMP managers? It depends on what you need. In my experience, only larger shops tend to use the SNMP managers; they tend to be expensive, resource intensive, and complex to install and maintain. Of course, SNMP managers also provide you with lots of information. In particular, the SNMP managers will provide you service-level information—that is, not only will they tell you whether the resource is “up” but also how fast it responds, how many bytes of resources are left, and so on. This makes SNMP managers very valuable if you’re looking to optimize your network. SNMP managers are excellent for keeping long-term track (baselining) of how your network and resources look on a normal day. As you’ll see in Hour 23, baselining is a very important part of problem determination when, as they say, “The network is slow!” After all, if you don’t have a sense of how things typically are, how can you tell when something is out of range? Long-term service-level record keeping is also a way to know—and a way to show your boss—that everything is operating efficiently and is working properly. Still, simple network polling packages can be extraordinarily effective, even for large shops, but particularly for smaller shops. They’re typically inexpensive compared to the costs of deploying even a modest SNMP installation, and they’re very easy to configure and use. Although most network polling packages don’t address service-level issues, look for more of them to do so in the future. Of course, you’ll never have the rich level of information that SNMP provides, but you might not need it. In short, a polling package is a one-stop application where you can monitor many services easily. Figure 22.3 shows one of them.
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To access the contents, click the c
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Workshop Q&A Quiz Answers to Quiz Q
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Eminent Domain TCP/IP Graffiti DHCP
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Configuring Your Proxy Proxy Troubl
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Socks Stuff AOL Instant Messenger A
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Table of Contents Introduction: Get
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about your more complex network iss
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Tell Us What You Think! Table of Co
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with me when I was first getting st
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NIC (network interface card) The te
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MAC Attack Previous Table of Conten
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Routers Previous Table of Contents
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technology as the future of local a
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for a TCP/IP address in a large net
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Sprechen Sie DLC? Previous Table of
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socket 80 of the TCP/IP address 167
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program in a name entry; entering t
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WINS Previous Table of Contents Nex
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kind and spit them out as fast as p
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Previous Table of Contents Next Hou
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Figure 2.1 A simple logical map. If
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Figure 2.4 A physical documentation
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the room). This way, you can read t
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un on the server at 9:50 on Monday
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Previous Table of Contents Next Par
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Beware of Vendor Your vendor probab
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call the risk/benefit ratio—the a
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Workshop Q&A Previous Table of Cont
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If you determine that it’s just o
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(see Figure 4.2). Figure 4.2 An Eth
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Division of Labor Previous Table of
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just that the network itself is at
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A Each situation is obviously diffe
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Ruling out is particularly effectiv
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Drive duplication can be a big help
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Previous Table of Contents Next Aft
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5. When you log problems on a given
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if they have a plan, they are going
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Is It a Virus, Doc? Previous Table
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O: Only have tried two other Intern
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A Remember that what a user says is
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Previous Table of Contents Next Loo
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Figure 7.1 Searching several sites
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You’ll also find forums run by th
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Previous Table of Contents Next
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a server but you think it should be
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Workshop Q&A Previous Table of Cont
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Name Brand Versus Generic PCs The c
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static electricity that may have bu
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SIMMs and DIMMs There are two kinds
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This is called looping back, becaus
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Windows Previous Table of Contents
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Figure 8.4 The NT Task Manager’s
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UNIX Previous Table of Contents Nex
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Probably the most important thing t
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Hour 9 Ethernet Basics Previous Tab
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which translates into lots of colli
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it currently requires fiber-optic c
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designation is simply an industry-s
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Down, Down, Down Previous Table of
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A Collisions cause other errors, su
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Follow the Rules: Share and Enjoy!
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Previous Table of Contents Next Err
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Token Analyzers Finding a NAUN is r
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Token-Ring does not have any hard-a
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Down Town Previous Table of Content
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C. 1, 16 D. 4, 16 Answers to Quiz Q
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Going Native Although Windows allow
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Eminent Domain Previous Table of Co
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machine with the username Administr
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protocol. They therefore relied on
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Previous Table of Contents Next Fol
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Most of the time, you’ll not want
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allows you to manage them and check
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Binding Previous Table of Contents
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Figure 11.6 Showing bindings for al
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Informational Commands Previous Tab
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Figure 11.8 A monitor session. We k
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case you need them. 2. What does SM
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a great example of client/server. W
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Previous Table of Contents Next Alt
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The first number is the process ID
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tcp 0 0 frotz.frob.com.telnet 200.1
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Name Game Previous Table of Content
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The next thing you need to find out
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A UNIX security and file permission
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the amount of time used or data sen
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NLMs In addition to accepting comma
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NLM Party Previous Table of Content
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Again, make sure you are running th
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Big Monitor Is Watching Previous Ta
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Then, eureka! During one session of
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Protocol Problems Previous Table of
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Figure 13.10 UNICON will configure
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Summary Previous Table of Contents
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7. The TCP/IP protocol and basic se
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ivory-tower stuff, but some of it i
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Configuring in Comfort Previous Tab
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Router 1 in Figure 14.3 is shown in
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to that network. Instead, the next
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Route in Peace: Routing Protocols P
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get to a network segment that until
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Figure 14.4 How two stations talk v
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Tree Trunks Previous Table of Conte
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garbage characters like these on a
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A. Add Router 99 to Router 88’s r
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Let’s lay out some definitions he
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Packet-Filtering Routers Previous T
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eceptionist hangs up one line (the
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from the proxy server without causi
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Proxy Trouble Previous Table of Con
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3. The proxy server resolves the na
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Q My vendor says that its firewall
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• Make checklists of tasks that m
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Joe User Previous Table of Contents
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groups | grep -q -w network && { ec
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If you’re going to add or replace
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Policies Previous Table of Contents
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in this hour—will pay off as you
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Q Which duplication software is rig
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Hour 17 Where Do I Start? Previous
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As optimistic as we’d all like to
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• PCAnywhere • ReachOut • Rem
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IPX/SPX Previous Table of Contents
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Q What happens if I ping the loopba
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correlations? A. netstat -a B. trac
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equire that the application files t
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The File and Print Blues Previous T
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With five potential points of failu
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In some cases, a slight difference
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Application Celebration Previous Ta
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Proto Local Address Foreign Address
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printer 515 Line Printer Daemon (ne
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Connected to 167.195.160.6. Escape
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Workshop Q&A Q What in the blazes i
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3. A 4. B 5. False 6. B 7. True 8.
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Intranet = Internal The word intran
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Page 307 and 308: 3. What does DMZ stand for? A. DNS
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Page 323 and 324: scantily, and still others are not
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Page 333 and 334: creating a segment between the swit
Page 335 and 336: Q Where can I get an Ethernet mini-
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Page 361 and 362: Q About that latency analysis metho
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Page 375 and 376: C. SYS:SYSTEM\AUTOEXEC.BAT D. SYS:P
Page 377 and 378: active hub An active hub is one tha
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An essential part of a network inte
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Index Symbols A 100 Megabit Etherne
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C new product, 45-46 burned-in addr
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DLC (Data Link Control), 17 DMZ (de
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F fat finger factor, 42-43, 46 fata
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ICQ, 335-336 IMAP (Internet Mail Ap
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M filters, 347-352 LANDecoder, 347
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NetBIOS (Network Basic Input/Output
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network card. See NIC Network Contr
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power supply check, 66 troubleshoot
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Q-R qualitative problems, 58 quanti
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names, 393-394 NetWare, 202 paging
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T dumb terminal mode, 211, 224 full
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isolating soft errors, 135-136 LANa
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U standardizing configuration, 245
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V W upstream, 134 Usenet newsgroups
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autodetection problems, 159 broadca
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